Examples of attic ladders or “disappearing stairways” are shown, for example, in U.S. Pat. Nos. 2,649,237 and 2,852,176. These ladders normally fold and retract upwardly into a frame secured between adjacent joists of the attic, and the folded ladder is covered by a door which normally extends substantially flush with the finished ceiling of the room in which the ladder is mounted. Attic ladders thus take up no floor space except when actually extended and are also inexpensive to construct, as compared with fixed stairways typically constructed on-site.
U.S. Pat. No. 4,281,743 issued to Fuller on Aug. 4, 1981 shows another conventional attic ladder. As shown in FIG. 1 attic ladder 11 includes an outside frame 12 mounted between adjacent floor joists 13 of the attic floor 14. Cross braces 15 are mounted between a pair of adjacent floor joists 13 to provide end support for the frame 12 of the disappearing stairway. Ladder 11 is mounted in the ceiling by securing frame 12 to the joists 13 and the cross braces 15. A cover panel 16 forms part of ladder 11 and is hinged to the outer frame 12, so that the door becomes substantially flush with the ceiling 17 when the ladder 11 is folded. A first ladder portion 17 is affixed to the inner face of cover panel 16 and a second ladder portion 18 is pivotally hinged to the first ladder portion so as to be unfolded or folded when the ladder is opened or closed. While commercially available attic ladders or disappearing stairways typically come in a number of sizes, most come in several standard widths and lengths adaptable to fit conventional constructions.
U.S. Pat. No. 4,541,508 issued to Lundh on Sep. 17, 1985 shows yet another conventional attic ladder. In FIG. 2, a foldable ladder is shown to consist of a lower section 11, a central section 12 and an upper section 13. The central section 12 is hingedly connected to the two remaining sections 11,13 by a hinge so that the central section 12 and the lower section 11 can be folded up on the upper section 13. Upper section 13 is hingedly attached to a frame 14 by hinges 15, with the folding down movement of the upper ladder section 13 being limited by a pair of toggle joints 16,17, attached to the upper ladder section and to the frame 14. Toggle joints 16,17 are rigidly connected to each other at the lower arms by means of an axle 18 extending in parallel with the rungs of the ladder and are attached to the axle outside the side rails of the ladder. The ladder is spring-biased to a closed position by a gas spring 19 connected at one end to an outside of one side rail and connected at its other end, via piston rod 19a, to moment arm 18a, which is rigidly connected to the axle 18 at such an angle that a maximum moment is generated when the door is almost entirely closed. When the point of connection between the gas spring 19 and the moment arm 18a has passed the line for moment center (i.e. the connecting line between the attachment of the gas spring 19 to the ladder 13 and the axle 18, which passing takes place when the door is opened entirely), the gas spring 19 actuates the door so that it is locked in folded-down position, which is necessary because the “weight” of the door decreases as soon as the ladder sections are folded out.
As far as methods of installation are concerned, a typical method of installation of the folding ladder is shown in FIGS. 3(a)–6(b), described below.
FIG. 3(a) shows preparation of an opening 51 to receive a folding ladder, such as in an attic. An area is selected that is clear of wiring and plumbing and a rough opening is cut for the ladder next to at least one joist 50. A sub-frame is then created on-site using lengths of wood cut to fashion headers/footers 52 and spacers 54. FIG. 3(b) shows headers/footers 52 nailed to joists 50 at both ends and to the joist that was cut. Spacers 54 are nailed to the headers/footers 52 and an adjoining joist 50. The ladder's frame box 58 will be attached to this sub-frame.
FIG. 4(a) shows installation of temporary support brackets 56. Temporary support brackets are formed from pieces of wood, such as 5″×5″ pieces of wood, attached to the ceiling at each corner of the opening by screwing them into the ceiling joists 50. A kit-made frame box 58 is assembled and lifted up through the opening 51 and then lowered to rest on the temporary support brackets 54. FIG. 4(b) shows attachment of the frame box 58. Shims (not shown) are used to center the frame box 58 in the subframe and to make sure it is level. The frame box 58 is then nailed to the sub-frame at a variety of points to secure the frame box and the temporary support brackets 56 are removed. The hatch door 62 is then attached to the frame box by a hinge 61 in such a manner as to provide a hatch that closes flush with the ceiling.
FIG. 5(a) shows both the installation of an individual wooden step 64 in a corresponding pair of grooves 65 in the left and right ladder rails 66, 68 and installation of all of the wooden steps 65 in the corresponding pairs of grooves in the left and right ladder rails, such as by inserting screws through the outside of the left and right ladder rails and into the steps. FIG. 5(b) shows the assembled folding ladder being folded about hinges 86, in the directions of the arrows, for installation. FIG. 5(c) shows that the folded ladder 70 is tied together with a string or strap 72 to prevent inadvertent unfolding of the ladder during installation. Following this step, a hand rail is attached to the uppermost (as-installed) ladder rail sections with a metal bracket and lower hanger arms are attached to selected ladder-to-hatch brackets 74.
FIG. 6(a) shows the conventional folding ladder assembly 70 following attachment of the folding ladder assembly to the hatch door 62 via ladder-to-hatch brackets 74. To set the ladder angle a string 75 is tied to a ladder step and is secured, at another end, to a footer portion 52 of the frame box 58 or support frame, as shown. A length of this string 75 is selected so as to provide and maintain the folding ladder at a desired angle during cutting of the ladder 70 to form a ladder foot 80. Alternatively, a second workman may hold the ladder at the desired angle during the ladder foot formation step. To create a foot 80 that is level with the floor, measuring sticks are used (labeled herein as “A” and “B” for descriptive purposes). Stick “B” 77 is placed on the front side of the ladder rail's second section 78 and stick “A” 76 is placed on the back of the ladder rail's third section 79, keeping the bottom of the stick level with the bottom of the rail (e.g., 66). A horizontal line may then be drawn across the rail (e.g., 66) that joins the marks on sticks “A” and “B” 76, 77 to denote the appropriate angle and the sticks 76, 77 are then translated up the ladder rails to intersect a lower portion of the lower ladder rail 79 and the horizontal line is transferred to the lower portion of the lower ladder rail. The sticks 76, 77 may also be used to determine an appropriate length of the lower portion of the lower ladder rail 79. The lower portion of the lower ladder rail 79 is then cut to form the foot.
FIG. 6(b) depicts downward rotation of the upper hanger arms 60, which are spring-loaded, and connection thereof to the lower hanger arms 85 at joint 87 to complete the conventional folding ladder assembly 70. Finally, an eyebolt, rope, or some other access device may be installed so as to protrude from, or to be accessible from, an underside of the hatch, to thereby permit a person in the space below the ladder to rotate and open the hatch and the folding ladder by means of, for example, a hook.
However, additional improvements can be realized in the structure of the attic ladder support frame as well as the methods by which the attic ladder is installed. Efficiency and man power improvements can also be realized, as the conventional methods of installation require two people to assemble the ladder.